Apparatus and method of oil polishing



Jan. 31, 1956 c. c. CONLEY 2,732,669

APPARATUS AND METHOD OF OIL POLISHING Filed 001;. 31, 1952 15:22:55. IIZLUT Char/e5 G 622216;;

United States Patent O ce 2,732,669 APPARATUS AND METHOD OF OIL POLISHING Charles C. Conley, Detroit, Mich., assignor to Houdaille- Hershey Corporation, Detroit, Mich., a corporation of Michigan Application Octoberlal, 1952, Serial No. 317,357 8 Claims. (Cl. 51-141) The present invention relates to the polishing of a flat metal workpiece with suitable moving abrasive-surfaces means, and more particularly, to the use of a polishing belt and an improved method and means for the operation thereof.

One of the most important applications of the instant invention is in connection with polishing machines in which substantially flat metal workpieces to be polished are fed between an abrasive surfaced belt backed by a contact roller and an idler roll. In many conventional polishing machines, the workpiece is fed by means of positively driven feed rollers between the abrasive-surfaced belt and the idler roll, and thecontact roll resiliently and drivingly urges the abrasive belt against theworkpiece. ,The endless abrasive-coated belt or Web is trained about the driven contact roll, and the contact roll is driven at a relatively high velocity so that the polishing is effected by pressure contact between the abrasive paper or cloth belt trained about the contact roll and the surface of the workpiece.

After prolonged polishing operations, the surface'of the contact roll, which is ordinarily made of rubber or other resilient material, becomes deformed, or distorted, and thus out of true surface alignment with the idler roll. Since efficient polishing requires that the contact roll be in true surface alignment with the backing or idler roll, the deformation or distortion of the surface of the contact roll after prolonged use necessitates shut-down of the equipment and resurfacing of the contact roll.

Also, it is particularly desirable to carryout the instant polishing operation in the presence of a suitable oil, for lubrication, temperature control and the like. Such oil must, of course, be applied to the abrasive belt and the surface of the workpiece, so that it may be interposed ,therebetween during the polishing operation. Such application of the oil also necessitates the presence of oil between the driven contact'roll and the abrasive belt which should be driven by the contact roll. The lubricating effect of the oil between the abrasive belt and the contact roll is, or" course, undesirable since excessive slippage between these two members is not desired. In addition, the use of pleats orsome other form of special design upon the surface of the contact roll in order to effectively increase the frictional drag between the contact'roll and the abrasive belt leaves much to be desired, since such special designs are rapidly lost during operation, as a result of abrading' action between the contact roll and the belt and/or as a result of the resurfacing operation of the contact roll which is periodically required. Resurfacing of the contact roll coupled with the additional step of imprinting or forming some special design thereon for improving the frictional properties is not economically practicable; nor is it an answer to the fluctuations in the frictional coaction between the belt and the contact roll which result from abrading of the roll during operation. a

It is, therefore, an important object of the present in- 2,732,669 Patented Jan. 31, 1956 piece with an abrasive belt, that comprises the steps of interposing oil between the abrasive belt and the workpiece and contacting the back of the belt with a driven roll surfaced with a resilient matrix having embedded therein minute discrete particles of a non-corrosive crystalline salt readily released from said matrix when exposed to the oil, whereby friction-increasing pockets are formed on the contacting surface of the roll.

It is another object of the present invention to provide an improved roll for drivingly urging an abrasivesurfaced polishing belt against a metal workpiece in the presence of oil, comprising a resilient peripheral roll portion adapted to contact the belt and having embedded therein minute discrete particles of a non-corrosive crys talline salt readily released from said matrix when exposed to the oil, whereby friction-increasing pockets are formed on the contacting surface of the roll.

It is still a further object of the present invention to provide an improved process of polishing a flat metal workpiece with an abrasive belt, that comprises the steps of contacting the back of the belt with a driven roll surfaced with a resilient matrix having embedded therein minute discrete particles of a non-corrosive crystalline salt, abrading said roll surface to expose some of said particles, and applying lubricating oil to said belt to lubricate the polishing and to release exposed particles from said surface to create minute friction-increasing suction cups on the roll surface.

Yet another important object of the instant invention is to provide an improved assembly for polishing a flat metal workpiece, that comprises an abrasive belt adapted to contact the workpiece, means for interposing lubricating oil between said belt and workpiece, a driven roll urging the belt against said workpiece, and friction drive means on said roll defined by a resilient matrix.

Other and further objects, features and advantages of the instant invention will become apparent to those skilled in the art from the following detailed disclosure of preferred embodiments thereof.

The general aspects of the instant polishing assembly are more or less conventional in the polishing art, in that a substantially fiat metal workpiece is moved along in a generally horizontal direction, for example, by means of pinch rolls positioned on opposite sides of the region in which polishing of the workpiece takes place. The workpiece is thus suspended in this region between pairs of pinch rolls and is supported from beneath by an idler roller, usually resiliently mounted. Directly above the idler roller and above the workpiece resting upon such roller there is suitably positioned the contact roll, which is connected to a motor for driving the same. An abrasive material, such as a cloth or paper web in the form of an endless belt having abrasive particles embedded on its outer surface is looped about the contact roll and about other rollers positioned thereabove for suitably tensioning the belt.

During operation, substantially flat plates of metal or the like workpieces are fed between the moving abrasive belt and the idler roller positioned therebeneath. The pinch rolls determine the linear velocity of the workpiece. The abrasive belt is resiliently urged against the workpiece by the contact roll which also frictionally engages the back of the abrasive belt so as to drive the same at a relatively high speed.

Preferably, suitable means are provided for the application of lubricating polishing oil, so as to interpose the same between the abrasive belt and the workpiece. Such means include suitable flow means or sprays for urging the oil in the direction of the nip between the abrasive belt and the workpiece. Such means also include suitable retainer walls near the region of this nip for preventing the unnecessary spread of the oil over the other parts of the appartus, and also suitable splash guards for cooperating with the traveling abrasive belt to prevent unnecessary splashing of oil therefrom during operation.

The general structural arrangements of the instant polishing apparatus, and particularly the cooperation between the pinch rolls, the idler roller, the workpiece, the abrasive belt, and the driven contact roll are understood by those skilled in the art, and are disclosed in additional detail, for example, in Charles H. Boehm application Serial No. 218,751, filed April 2, 1951, which is copending herewith and assigned to the assignee of the instant application.

A further description of the present invention is made in connection with the attached sheet of drawings in which:

On the drawings:

Figure 1 is a fragmentary view of a polishing apparatus with parts in elevation, illustrating the apparatus in position to effect polishing of a substantially flat piece of metallic stock;

Figure 2 is a slightly enlarged view of the assembly illustrated in Figure 1, illustrating the condition of the apparatus during the resurfacing or trueing of the contact roll;

Figure 3 is a side elevational view of the contact roll shown in Figures 1 and 2; and

Figure 4 is a fragmentary cross-sectional view taken substantially along the line IVV of Figure 3.

As shown on the drawings:

The system of Figure 1 includes a more or less conventional polishing assembly and illustrates the position of the elements during the polishing operation. In that assembly, reference numeral denotes a frame assembly which carries a drive motor 11. A shaft 12 of the motor carries a sprocket 13, about which is trained a chain 14 for driving a sprocket wheel 15 on a resiliently covered contact roll 16.

The frame member 10 also supports an idler tensioning roller 17 by means of a pivotally movable arm 18, and a second idler roller 19 at the top of the frame member 10. An abrasive material, such as a paper web containing abrasive particles embedded in its outer surface, is trained around the contact roll 16 and the idler rollers 17 and 19 in the form of an endless loop. The proper tension on the web 20 is supplied by adjusting the position of the idler roller 17 by varying the angular position of the arm 18.

In operation, substantially flat plates of metal 22 are fed between the moving abrasive web 20 and a rigidly journaled backing or idler roll 23. Suitable means 42 are provided for adjusting and maintaining the desired contact pressure between the abrasive web 20 and the plates 22. Each plate 22 is fed positively between the contact roll 16 and the idler roll 23 with a predetermined linear velocity by means of a pair of coacting pinch rolls 25 and 26 preceding the contact roll 16, and a pair of pinch rolls 27 and 23 beyond the contact roll assembly. The pair of pinch rolls 25 and 26 is driven by a motor 30 through a sprocket wheel 31 and a chain and sprocket drive 32 interconnecting the pinch rolls 25 and 26. In a similar manner, the pinch rolls 27 and 28 are positively driven by a motor 34 through a sprocket wheel 35 and an interconnecting chain and sprocket drive 36.

The addition of suitable means 43 for flowing or spraying oil upon the traveling workpiece just prior to the entrance into the nip defined by the workpiece and the abrasive belt in the structure just mentioned is, of course, well within the skill of the art, and need not be further discussed herein.

The instant invention is particularly applicable to such polishing operations wherein oil is employed as described. The use of oil for this purpose is particularly advantageous, as was mentioned hereinbefore, but the presence of oil particularly complicates the cooperation between the contact roller and the abrasive belt. In fact, in actual operation it has been found that, prior to the instant invention, it was necessary to use expensive and specially prepared cloth belts in order to obtain the necessary frictional engagement between the contact roller and the belts during such oil-polishing. The instant invention, however, provides a unique and significant advance in the oil-polishing art, permitting the use of ordinary, inexpensive paperbacked abrasive belt or Webs, and also providing a new and inexpensive contact roll structure and composition for effectively cooperating with such abrasive belts or webs.

One important aspect of the instant invention involves carrying out the polishing process upon a flat metal workpiece with an abrasive belt, while interposing oil between the belt and the workpiece, by contacting the back of the belt with a driven contact roll 16 that has a shaft 16a covered or surfaced with a resilient matrix 16b having embedded therein minute discrete particles 44 of a noncorrosive crystalline salt which is readily released from the matrix 16b when exposed to the oil. The effect of the release or removal of these individual salt particles 44 from the matrix 16b, upon their being exposed at the matrix surface, is the creation of friction-increasing pockets 45 or minute suction cups formed upon the contacting surface of the roll.

As was explained previously, a certain amount of abrading of the contact roll surface takes place during ordinary operation, in conjuction with the deformation and the like wear and tear phenomena which effect the roll, and in the case of the instant roll such abrading has a unique effect. As would be expected, abrading of the roll surface tends to remove the minute suction cups previously formed, but such abrading also tends to open other additional minute chambers within the resilient matrix, so as to expose those chambers and the salt therein to the general conditions of wear and tear upon the roll surface and to the presence of the lubricating oil. The matrix is, of course, made of rubber or the like resilient material which is incapable of forming a truly adhesive bond at the surface of rigid crystalline particles embedded therein. Moreover, the presence of the oil effectively lubricates the relative movement between such articles and the resilient matrix, so as to assist in the release of such crystals from the surface of the resilient matrix, so as to recreate minute surface pockets and continuously replenish the number of such minute suction cups placed upon the roll surface.

A particularly important aspect of the invention resides in the use of crystalline non-corrosive salts. Certain salts are highly corrosive (with respect to the metal workpieces here employed) and their use in a structure such as that here involved would, of course, subtract appreciably from the advantages here obtained. The use of crystalline (as contrasted to amorphous) materials is also very important, since it is necessary to have the benefit of the strength of such hard crystalline materials that are still embedded within and covered over by the resilient rubber matrix. While still covered by the matrix, these minute crystals serve somewhat in the manner of fillers to impart additional strength to the rubber matrix, and more particularly to impart uniform strength thereto, which could not be obtained if the various minute chambers within the rubber matrix were filled with soft amorphous particles or particles which vary in their hardness. The crystalline rigid character of these particles is of critical importance for still another reason, namely, the prevention of appreciable cohesion between the rubber matrix and the individual particles. It will be appreciated that during operation of the contact roll compression forces at a given local region in the roll periphery are constantly changing, so that the resilient material is constantly loading and unloading in response to such forces. This repeated loading and unloading tends to cause the rubber matrix to pull away from the individual crystalline particles, which will not deform therewith, and the net result is that the individual particles are readily releasable from the matrix by the time the matrix is abraded or resurfaced down :to the particular chamber containing such individual particles.

It is also particularly advantageous in the practice of tthe instant invention, if the particular crystalline salt employed is oil-soluble (or oil-dispersible) so as to facili- :tate the release of the salt particles from the rubber matrix as well as facilitate the removal of the individual particles from theoperating region. Although the individual particlesare extremely small in size, it is not desirable to have theinirtain their solid crystalline form once they have been released from the rubber matrix. In the case of many abradingoperations, the oil employed contains an appreciable amount of water, which is advantageous from the point of view of the instant invention because such water and oil combination would be particularly effective in'dissolving or dispersing any of the crystalline non-corrosive salts which would ordinarily be used in the practice of the instantinvention. In any event, it is preferred to employ a salt that is soluble (or dispersible) in the lubricant, and, if the lubricant contains water as well as oil the number of preferred salts is substantially increased.

In compounding the instant contact roll resilient matrix, certain features have been found to be particularly important. First, the amount of salt employed may range from a minimum amount necessary to impart an appreciable advantageous effect upon the resilient matrix, which is about 10 weight percent of the matrix, to a maximum amount above which the resilient matrix properties are no longer improved and may be impaired with respect to resilience, which is about 50 weight percent of the matrix. Most preferably, in the case of the customarily used rubber matrix, the portion of salt is about 20-30 weight percent of the matrix.

In compounding the salt and rubber, it is important to ultimately obtain a continuous rubber phase or matrix, having the salt particles embedded therein in separate and distinct chambers within the matrix. If such chambers or pores were interconnecting, it might be possible for the oil to effectively leach substantial quantities of the salt out of chambers well within the body of the rubber matrix, so as to alter appreciably the strength of the matrix. matrix may be carried out by milling the salt into suitable unvulcanized rubber and then forming the rubber in the desired annularly cross-sectioned or sleeve-like shape of the contact portion of the contact roll, and then vulcanizing the rubber to the extent desired. In general, it is preferable to have a Durometer A hardness of 40-90, and most preferably of 65-75.

Another important object of the instant invention resides in the use of extremely small particle sizes, preferably within the range of 0.01-0.125 inch (which is the maximum dimension or assumed diameter of such particles). Most preferably the average particle size is about 0.03 inch. It will be appreciated that the particular function of providing minute suction cups by the removal of such particles effectively controls the permis- ..sible particle size. In this respect, the contact (land area) at which the compression load is applied directly to the workpiece (through the abrasive belt) must be such that the width thereof is at least more than twice the maximum particle size. Ordinarily the contact area is of .appreciable size, however, since the usual dimensions for In this respect, the compounding of thesuch a roll are approximately 6 inches in diameter and about 30 inches long.

Whenever the instant roll is resurfaced, there is a tendency to obtain a relatively smooth surface, in the absence of the oil, since the usual resurfacing operation is not particularly effective in removing the salt particles from those chambers exposed during the resurfacing. It will be appreciated that a brief oil treatment and/or a brief wire brushing operation upon the surface of the reconditioned roll very readily creates the necessary small surface voids or pores.

The salts which I prefer to use in the practice of my invention include sodium pyrophosphate, potassium sodium tartrate, sodium thiosulfate and sodium ferrocyanide. It will, of course, be appreciated that other salts having the necessary properties hereinbefore disclosed may be used in the practice of the invention. It has been found that sodium pyrophosphate is most preferred for use in the instant invention; however,- on certain'special occasions, particularly involving peculiar oil-solubility problems, it would be found to be preferable to employ salts of organic acids,,particularly the alkali metal salts thereof, which have a suitably strong crystalline structure.

As an example of the improvements effected in accordance With the instant invention, it should be pointed out that under actual operating conditions it was determined that a commercially available paper-resin abrasive belt gave the following slippage test results using a plain rubber contact roll and applying the horsepower loads indicated below:

Result Load Efficiency, Slippage, percent percent The foregoing results clearly demonstrate that under commercial operating conditions for oil-polishing the specific belt here tested could not be used with a load of more than 18 horsepower per foot. Under substantially the same operating conditions, however, a rubber contact roll embodying the instant invention, having 20 weight percent of the matrix of sodium pyrophosphate crystals embedded therein, operated at 98.71% efiiciency (and 1.79% slippage) at the 20 horsepower load, and operated at 96.13% efiiciency (and 3.87% slippage) at the 30 horsepower load, thereby demonstrating clearly the superiority of performance of the instant roll.

It will, of course, be understood that various details of construction and composition may be varied to a wide range without departing from the principles or scope of the instant invention.

I claim as my invention:

1. In a process of polishing a fiat metal workpiece with an abrasive belt, the steps of interposing oil between the abrasive belt and the workpiece and contacting the back of the belt opposite the workpiece with a driven roll to drive the belt, said roll being surfaced with a resilient matrix having embedded therein minute discrete particles of a crystalline salt readily released from said matrix when exposed to the oil, whereby friction-increasing pockets are formed on the contacting surface of the roll.

2. In a process of polishing a fiat metal workpiece with an abrasive belt lubricated by oil, the step of contacting the back of the belt opposite the workpiece with a driven roll to drive the belt, said roll being surfaced with a resilient rubber matrix having embedded therein minute discrete particles of a crystalline salt readily released from said matrix when exposed to the oil, whereby friction- 7 increasing pockets are formed on the contacting surface of the roll.

3. In a process of polishing a fiat metal workpiece with an abrasive belt lubricated by oil, the step of contacting the back of the belt with a driven roll surfaced with a resilient rubber matrix having embedded therein 10-50 weight percent thereof of sodium pyrophosphate crystals of 0.01-0.125 inch particle size.

4-. In a process of polishing a flat metal workpiece with an abrasive belt, the steps of interposing oil between the abrasive belt and the workpiece and contacting the back of the belt with a driven roll to drive the belt, said roll being surfaced with a resilient matrix having embedded therein minute discrete particles of an oil-soluble, crystalline salt, in particle sizes of 0.01-0.125 inch.

5. In a process of polishing a fiat metal workpiece with an abrasive belt, the steps of interposing oil between the abrasive belt andthe workpiece and contacting the back of the belt with a driven roll to drive the belt, said roll being surfaced with a resilient rubber matrix having embedded therein 10-50 weight percent thereof of discrete 0.03 inch-sized particles of oil-soluble crystals.

6. In a process of polishing a flat metal workpiece with an abrasive belt, the steps of contacting the back of the belt with a driven roll to drive the belt, said roll being surfaced with a resilient matrix having embedded therein minute discrete particles of a crystalline salt, abrading said roll surface to expose some of said particles, and applying lubricating oil to said belt to lubricate the polishing and to release exposed particles from said surface to create minute friction-increasing suction cups on the roll surface.

7. A contact driving roll comprising an annularly cross-sectioned'contact portion composed, of a rubber matrix having embedded therein 10-50 weight percent thereof of discrete 0.01-0.125 inch size particles of sodium pyrophosphate. 8. In an assembly for polishing a flat metal workpiece, an abrasive belt adapted to contact the workpiece, means for interposing lubricating oil between said belt and workpiece, a driven roll driving said belt and urging the belt against said workpiece, and friction drive means on said roll engaging said belt and defined by a resilient matrix peripheral contact portion having therein a plurality of minute chambers, those chambers within said matrix being filled with hard salt crystals to impart strength to the matrix and those chambers on the roll surface defining a plurality of minute suction cups to increase the frictional coaction between the roll and the belt.

References Cited in the file of this patent UNITED STATES PATENTS 1,563,943 Adams et a1. Dec. 1, 1925 2,145,418 Herchenrider Jan. 31, 1939 2,332,329 Maca Oct. 19, 1943 2,367,107 Emmons Jan. 7, 1945 2,378,643 Losey June 19, 1945 2,407,939 Steinhilber Sept. 17, 1946 2,431,795 Elmes Dec. 2, 1947 2,527,003 Emmons Oct. 24, 1950 2,562,229 Bell July 31, 1951 

8. IN AN ASSEMBLY FOR POLISHING A FLAT METAL WORKPIECE, AN ABRASIVE BELT ADAPTED TO CONTACT THE WORKPIECE, MEANS FOR INTERPOSING LUBRICATING OIL BETWEEN SAID BELT AND WORKPIECE, A DRIVEN ROLL DRIVING SAID BELT AND URGING THE BELT AGAINST SAID WORKPIECE, AND FRICTION DRIVE MEANS ON SAID ROLL ENGAGING SAID BELT AND DEFINED BY A RESILIENT MATRIX PERIPHERAL CONTACT PORTION HAVING THEREIN A PLURALITY OF MINUTE CHAMBERS, THOSE CHAMBERS WITHIN SAID MATRIC BE- 